Performance of four genetic stocks of cage-housed White Leghorn hens grouped
according to differences in open-field behavior.
A. Bruce Webster, University of Georgia, Athens, GA
An attempt was made to identify divergent behavioral groups of pullets
and to monitor their subsequent behavior and production performance in
battery cages. One hundred chicks (week-old) from each of two pure lines
(33,99) and their reciprocal crosses (39,93) were tested individually for
4 minutes in an open-field environment consisting of a plywood box having
a 30 cm by 30 cm floor area. Visual and auditory records of behavior were
obtained on videotape. Residuals from ANOVA's of the latencies to peep,
head flick and walk were converted into standardized values by dividing
them by their respective standard errors. These values were summed to form
an index of the behavioral activation of each chick. At 19 weeks of age,
within each stock, the 40 surviving pullets which had ranked highest in
behavioral activation, and the 40 which had ranked lowest, were selected
as ACTIVE and INACTIVE birds, respectively. For each stock, pullets in
the same behavioral category were paired and housed in battery cages. Videorecords
of the behavior of half the hens were obtained at 31- 33 weeks of age.
The remaining hens were videorecorded at 45-47 weeks of age. Two sets of
ethograms were derived from these videorecords, one for a 2-hour period
in the afternoon when no eggs were laid, and the other for a half hour
before egg laying, with the prelaying bird identified. In general, the
major activities of hens during the non-laying period were not greatly
affected by open-field behavioral category. ACTIVE hens manifested significantly
higher levels of head flicking in stocks 33 and 93, but not in stocks 39
and 99. The number of instances in which a hen could not be observed tended
to be less for ACTIVE hens than for INACTIVE hens (P=.06). Although behavior
in the non-laying and prelaying periods was not compared by statistical
analysis, it was evident that prelaying hens manifested higher levels of
head flicking, standing, walking and bobbing/pacing, and lower levels of
preening. Prelaying ACTIVE hens did significantly less walking than their
INACTIVE counterparts. The only significant egg production difference between
ACTIVE and INACTIVE hens occurred during the first 28-day period of lay,
when ACTIVE hens averaged higher production (87.5% hen-day production vs
82%, respectively, P=.50). However, the production curves indicate that,
while ACTIVE hens had substantially higher early egg production than INACTIVE
hens in the pure-line strains, 33 and 99, this tendency was only slightly
evident in cross 39 and not evident at all in cross 93. The relationships
between behavioral characteristics of chicks in an open-field test and
behavior and production of the same birds as hens in battery cages, therefore,
are influenced by genetic stock. In the cases where early open-field behavior
was linked to subsequent behavior in cages, the ACTIVE hens appeared to
maintain greater alertness or arousal in cages, but also appeared to be
less disturbed by the egg-laying experience. Hybridization diminished the
relationship between open-field behavioral category and early-cycle egg
production.